This invention pertains generally to the art of joining aluminum alloy components by brazing and, it pertains in particlar to compositions used for vacuum brazing. For purposes of this application the term "vacuum" refers to environments where pressures are beolw 100 .times. .sup..sup.-3 torr and the partial pressures of water and oxidizing species, such as O.sub.2, are below 1 .times. 10.sup..sup.-4 torr and 8 .times. 10.sup..sup.-4 torr, respectively.
As is well known, aluminum alloys containing silicon are appreciated as useful compositions for brazing. Furthermore, it has been recognized that the addition of small amounts of magnesium makes such alloys suitable for vacuum brazing.
In accordance with the present invention, it has been found that a brazing composition consisting essentially of aluminum, silicon, magnesium and tin has especially desirable properties for purposes of vacuum brazing at relatively low pressures, such as below 1 .times. 10.sup..sup.-4 torr for example. About 0.1% tin is usually sufficient. For the particular advantages and benefits of the invention, reference is made to the tests and related results and discussion, which are set forth later below.